U.S. Pat. No. 4,883,265, titled "Tray Apparatus", filed Jul. 28, 1988, by Noriyoshi Iida, et al., discloses a device of the aforesaid kind for delivering, depositing, and aligning sheets in a stack container. The sheet deposition, sheet alignment, and sheet hold-down means are configured in combined fashion as at least a single toothed belt, configured in the form of an endless loop, having teeth arranged on its inner side. The toothed belt is arranged around a toothed pulley which is mounted centeredly on a drive pulley, located below, of a sheet in-feed roller pair of the sheet delivery means. The toothed belt, which projects with its free loop region into the stack container, is secured in position by means of a contact roller of the sheet in-feed roller pair on the one hand with its upper belt portion on the toothed pulley and by means of a rotation or circulation effected by means of the drive pulley, and on the other hand is pressed with its lower belt portion onto the sheet deposition surface or the sheet stack. In this context the free loop region of the toothed belt constitutes, with its outer side of its upper belt portion in the region of the toothed pulley, a transport surface running substantially horizontally and parallel to the sheet deposition surface for a sheet delivered by means of the sheet in-feed roller pair. For reliable transportation of the sheet, the outer side or transport surface has an elevated coefficient of friction. After it has been released by the sheet in-feed roller pair, the delivered or fed-in sheet, carried at its rear, end region by the upper belt portion, is fed farther into the sheet stack, lowered, and deposited onto the sheet deposition surface or onto the sheet stack. Because the sheet stack container is arranged with a downward tilt at its sheet deposition surface end which faces against the sheet delivery direction, the delivered sheet slides back, opposite to the sheet delivery direction, against the toothed belt which continues to circulate. The delivered sheet is thereby grasped by the lower belt portion and transported and aligned, opposite to the sheet delivery direction, against a front wall of the stack holder that is configured as a sheet stop and tilted against the sheet delivery direction. Arranged in the region above the upper belt portion is a pressure means which presses the delivered sheet onto the upper belt portion while it is being fed in.
It is disadvantageous that the delivered or fed-in sheet is not guided to the point of complete deposition or to the deposition surface during its lowering and deposition movement. In this case, an imprecise lateral alignment is possible as the sheets are being stacked. Furthermore, an inclined collection container is necessary in order to bring the delivered sheet once again into the region of influence of the tooth belt for alignment. The consequence of the latter, together with a longer in-feed path resulting from the toothed belt, is a longer sheet in-feed time. It is also disadvantageous that the toothed belt circulates continuously, which, when thin sheets are being aligned and held down, can lead to compression (creasing, waving, etc.) of the sheets at the sheet stop, or, regardless of the sheet thickness, to elevated material abrasion. A further disadvantage is that the toothed belt for aligning and holding down sheets does not act on the sheets at the outermost end of the delivered sheets or not directly at the sheet stop, which can result in the sheets being pushed up at the stop.
Therefore, a need persists for a device that can deliver, deposit and align sheets in a stack container that greatly reduces sheet in-feed time, virtually eliminates compression of the sheets while being easy to construct and operate, and is cost effecient to manufacture.